The objective of our research program is the elucidation of the physicochemical mechanism and the biological significance of interactions between steroid hormones and serum proteins that bind steroids specifically and with high affinity. The chemistry of the binding site in steroid hormone antibodies will be explored. The specific aims include studies with: a) human and cavian corticosteroid-binding globulin and cavian progesterone-binding globulin to elucidate the chemical structure of the steroid binding site, the mechanism of the association, and the significance of the carbohydrate constituents; b) antibodies against progesterone, steroid binding specificity and the chemical nature of the binding site of these immunoglobulins in comparison with the properties of the steroid binding site in high-affinity serum proteins. The methods used are those applied in the principal investigator's laboratory for many years, in addition to newly required or developed techniques.